NASA is celebrating 35 years of success with its Voyager 2 spacecraft, which is the longest-operating NASA space probe in history.

The Voyager 2 launched on August 20, 1977. It's main purpose is to study the outer solar system and eventually interstellar space, which NASA is still waiting on.

The Voyager 2 mission turned 35 years old yesterday, but the spacecraft actually became the longest-operating NASA probe on August 13 when it surpassed Pioneer 6. Pioneer 6 was the first in a series of solar-orbiting, battery-powered satellites that continually took measurements of interplanetary phenomena throughout different points in space. It launched December 16, 1965 and transmitted its last signal on December 8, 2000.

Voyager 2 has made a lot of progress in its 35 years in space, particularly in the way of Neptune, Jupiter, Saturn and Uranus exploration. It discovered the hexagonal jet stream in Saturn's north polar region, the geyser's on Neptune's moon Triton and the magnetic poles of Neptune and Uranus.

"Even 35 years on, our rugged Voyager spacecraft are poised to make new discoveries as we eagerly await the signs that we've entered interstellar space," said Ed Stone, Voyager project scientist at the California Institute of Technology. "Voyager results turned Jupiter and Saturn into full, tumultuous worlds, their moons from faint dots into distinctive places, and gave us our first glimpses of Uranus and Neptune up-close. We can't wait for Voyager to turn our models of the space beyond our sun into the first observations from interstellar space."

Voyager 1's anniversary is also quickly approaching. Voyager 1, which launched 16 days after Voyager 2, has also been exploring the outskirts of the solar system with intentions of entering interstellar space. In fact, Voyager 1 captured the fastest rate of changes on the edge of the solar system earlier this month, which are helpful indicators of whether Voyager 1 will soon cross out of the heliosheath and into interstellar space. Changes in charged particles around the sun and the direction of the magnetic field help to assess these changes.